1. Field of the Invention
The present invention relates to a synthetic resin composition which comprises a synthetic resin such as a urethane resin or epoxy resin used for public engineering works, and a specific granular filler.
2. Description of the Prior Art
It has been known to use synthetic resins such as urethane resins and epoxy resins in the field of public engineering works such as packing and bonding for gaps of slabs under tracks. However, these synthetic resins are remarkably expensive.
In order to improve the mechanical properties of these synthetic resins and to decrease the cost of these synthetic resins, it has been proposed to combine a filler with the synthetic resin. Howwever, the art has not succeeded to obtain a synthetic resin composition suitable for said purposes.
The inventors have studied on sintering treatments of various mineral fine powders and uses of the sintered products in various fields especially as fillers for synthetic resins, especially uses of sintered clay minerals.
The inventors have studied to prepare a sintered granular filler by an extrusion granulating method. Fine mineral powders such as clay, talc, kaolin, bentonite and diatomaceous earth are selected and mixed and the mixture of the fine mineral powders is kneaded with 15 to 20 wt.% of water and the resulting pasty mixture is extruded in a thread form through a metallic gauze under a desired pressure and cut for a length of 1 to 1.5 mm. The cut beads are tumbled in a rotary cylinder to form spherical beads and the spherical beads of the mineral are sintered at 800.degree. to 1,200.degree. C. to obtain sintered granular filler. The sintered granular filler can be used as the filler for a synthetic resin used in public engineering works. However, the bulk density of the filler is high and the mechanical properties of the resin composition are not satisfactory and the resin composition is expensive.